Review on 🔌 iUniker Power Switch for Raspberry Pi 3, Pi 2, B+, Zero W - 4-Pack, Raspberry Pi Power Supply Cord with On/Off Push Switch, MicroUSB Female to Male Cable by Jen Johnson

I've tried them on 2 and 3 B+. Both were connected to an external drive, Ethernet, USB mouse and HDMI. Without the switch both worked fine and never showed any low voltage flashes. As soon as I put the switch between the device and the power supply, they both flashed constantly. They either actually prevent enough current from being delivered to the device, or they simply don't allow the device to sense enough current. (The latter is doubtful.) Anyway, they're useless to me. I don't want to give up valuable voltage for the convenience of a switch.